Film evaluating method, temperature measuring method, and semiconductor device manufacturing method

ABSTRACT

Reference infrared-absorption spectrum patterns are prepared in advance as a database. The infrared-absorption spectrum pattern of a film targeted for measurement is measured using FT-IR spectroscopy. Subsequently, multivariate analysis is performed using PLS regression, based on the reference infrared-absorption spectrum patterns and the infrared-absorption spectrum pattern of the target film. The film-growing temperature and other factors are then computed in accordance with the analysis results.

TECHNICAL FIELD

[0001] The present invention relates to a film evaluation method, atemperature measurement method and a semiconductor device fabricationmethod, applicable to fabrication of various kinds of transistors andsemiconductor memories and other semiconductor devices that areincorporated into electronic equipment.

BACKGROUND ART

[0002] In recent years, as the degree of integration of, and theperformance of, semiconductor devices have been increasing,fluorine-doped silicon oxide films (hereinafter referred to as “FSGfilms”) having low relative dielectric constants are being used forinterlevel dielectric films in which multilevel interconnects areformed. Generally, an FSG film is grown in an HDP-CVD (high densityplasma-chemical vapor deposition) apparatus that is suitable for fillingof the fine interconnection vias.

[0003] The HDP-CVD apparatus, however, has a structure in which anelectrostatic chuck is employed to hold the wafer, and is thusencumbered by a problem in that the film-growing temperature cannot bemonitored. In addition, the film-growing temperature in the HDP-CVDapparatus, which is determined by factors such as RF power that isapplied during film growth, cannot be measured accurately because it isdifficult to measure the actual temperature using a silicon substratethat comes with a thermocouple, for example.

[0004] The present inventors therefore used the temperature measurementtechnique described in International Publication No. WO99/57146 tomeasure film-growing temperature in an HDP-CVD apparatus. In thistechnique, temperature measurement is carried out based on the rate atwhich a silicon amorphous layer on a silicon substrate is recovered.

[0005] Now, in addition to the foregoing international publication,which relates to spectroscopic ellipsometry, the following documents arerelevant.

[0006] (1) Nuclear Instruments and Methods in Physics Research, B19/20,(1987), pp. 577-581.

[0007] (2) Japanese Laid-Open Pat. Publication No. H06-077301.

[0008] (3) Siemens Forsch. -u.Entwickl. -Ber.Bd. 10, (1981), Nr. 1, pp.48-52.

[0009] (4) Japanese Laid-Open Pat. Publication No. H05-249031.

PROBLEMS THAT THE INVENTION INTENDS TO SOLVE

[0010] Nevertheless, the conventional temperature measurement techniquebased on the rate at which a silicon amorphous layer is recovered,requires advance preparations such as performing a procedure in whichthe amorphous silicon layer is formed on the silicon substratebeforehand. Further, in order to measure film-growing temperature in anHDP-CVD apparatus, operation of the HDP-CVD apparatus has to be stoppedmid-process to form a film under conditions exclusively for temperaturemeasurement. In other words, the CVD apparatus has to be placedoff-line.

DISCLOSURE OF INVENTION

[0011] An object of the present invention is to easily measure thecharacteristics or film-growing temperature of a film that has beenformed using a film-growing apparatus, without placing the apparatusoff-line, that is, without causing deterioration in the productivity ofthe apparatus.

[0012] An inventive film evaluation method includes the steps of: (a)irradiating with electromagnetic waves a substrate on which a film isformed, thereby measuring an absorption spectrum for the electromagneticwaves, and (b) calculating from the shape of the absorption spectrum aspecific value corresponding to the quality of the film.

[0013] According to the inventive method, since the characteristics of afilm can be detected using an electromagnetic-waves absorption spectrum,materials that can be used for film-growing apparatus control anddetermination of the quality of films, e.g., in semiconductor devices,can be obtained.

[0014] In the step (a), the electromagnetic waves may be infraredradiation, and in the step (b), the specific value may be calculatedfrom the shape of an absorption spectrum for the infrared radiation.

[0015] In that case, a plurality of reference infrared-absorptionspectra may be prepared in advance in accordance with film qualitylevel, and in the step (b), the reference infrared-absorption spectraand the infrared absorption spectrum of the film may be compared witheach other, thereby calculating the specific value. Then, the specificvalue can be obtained in an easy manner.

[0016] In the step (b), multivariate analysis may be performed based onthe shapes of the reference infrared-absorption spectra and of theinfrared absorption spectrum, thereby calculating the specific value.Then, the specific value can be calculated with high accuracy using PLS(partial least squares) regression or other techniques.

[0017] In the step (a), preferably, an infrared absorption spectrum ofthe substrate, which has been measured in advance, is subtracted fromthe infrared absorption spectrum of the film and the substrate, therebyobtaining an infrared absorption spectrum of the film alone.

[0018] An inventive temperature measuring method includes the steps of:(a) irradiating with electromagnetic waves a substrate on which a filmis formed, thereby measuring an absorption spectrum for theelectromagnetic waves, and (b) calculating from the shape of theabsorption spectrum a temperature at which the film has been grown.

[0019] According to the inventive method, since the film-growingtemperature of a film can be detected using an electromagnetic-wavesabsorption spectrum, materials that can be used for film-growingapparatus control and determination of the quality of films, e.g., insemiconductor devices, can be obtained.

[0020] In the step (a), the electromagnetic waves may be infraredradiation, and in the step (b), the temperature at which the film hasbeen grown may be calculated from the shape of an absorption spectrumfor the infrared radiation.

[0021] A plurality of reference infrared-absorption spectra may beprepared in advance in accordance with film-growing temperature, and inthe step (b), the reference infrared-absorption spectra and the infraredabsorption spectrum of the film may be compared with each other, therebycalculating the temperature at which the film has been grown. Then, thetemperature at which the film has been grown can be calculated easily.

[0022] In the step (b), multivariate analysis may be performed based onthe shapes of the reference infrared-absorption spectra and of theinfrared absorption spectrum, thereby calculating the temperature atwhich the film has been grown. Then, the temperature at which the filmhas been grown can be calculated accurately using PLS regression andother techniques.

[0023] In the step (a), preferably, an infrared absorption spectrum ofthe substrate, which has been measured in advance, is subtracted fromthe infrared absorption spectrum of the film and the substrate, therebyobtaining an infrared absorption spectrum of the film alone.

[0024] In the step (a), the substrate may be placed in a film-growingapparatus in advance, and the film is formed on the substrate, and inthe step (b), the temperature at which the film has been grown may becalculated as a temperature inside the film-growing apparatus. Then, thetemperature in the film-growing apparatus (chamber) can be quicklymeasured using an in-line wafer or a control wafer, without attaching asensor to the wafer or taking another measure.

[0025] A first inventive method for fabricating a semiconductor deviceincluding a film as an element forming the device, includes the stepsof: (a) forming the film on an underlying wafer placed in a film-growingapparatus, (b) irradiating with infrared radiation the wafer on whichthe film has been formed, thereby measuring an infrared absorptionspectrum, (c) calculating from the shape of the infrared absorptionspectrum a specific value corresponding to the quality of the film, and(d) controlling conditions determined for the film-growing apparatus, inaccordance with the specific value calculated in the step (c).

[0026] According to the inventive method, in-line non-destructivedetection of the characteristics of a film can be carried out using anelectromagnetic-waves absorption spectrum, and results of the detectioncan be used for film-growing apparatus control. Thus, specific valuescan be measured in all film growing processes without causing anydeterioration in productivity, thereby enabling conditions determinedfor a film-growing apparatus to be controlled.

[0027] A plurality of reference infrared-absorption spectra may beprepared in advance in accordance with film quality level, and in thestep (c), the reference infrared-absorption spectra and the infraredabsorption spectrum of the film measured in the step (b) may be comparedwith each other, thereby calculating the specific value. Then, theprocess steps can be controlled in an easy manner.

[0028] In the step (c), multivariate analysis may be performed based onthe shapes of the reference infrared-absorption spectra and of theinfrared absorption spectrum, thereby calculating the specific value.Then, process control can be performed accurately.

[0029] A second inventive method for fabricating a semiconductor deviceincluding a film as an element forming the device, includes the stepsof: (a) forming the film on an underlying wafer placed in a film-growingapparatus, (b) irradiating with infrared radiation the wafer on whichthe film has been formed, thereby measuring an infrared absorptionspectrum, (c) calculating from the shape of the infrared absorptionspectrum a temperature at which the film has been grown, and (d)controlling conditions determined for the film-growing apparatus, inaccordance with the temperature at which the film has been grown, thetemperature calculated in the step (c).

[0030] According to the inventive method, in-line non-destructivedetection of the temperature at which a film has been grown can becarried out using an electromagnetic-waves absorption spectrum, andresults of the detection can be used for film-growing apparatus control.Therefore, film-growing temperatures can be measured in all film growingprocesses without causing any deterioration in productivity, therebyenabling conditions determined for a film-growing apparatus to becontrolled.

[0031] A plurality of reference infrared-absorption spectra may beprepared in advance in accordance with film-growing temperature, and inthe step (c), the reference infrared-absorption spectra and the infraredabsorption spectrum of the film measured in the step (b) may be comparedwith each other, thereby calculating the temperature at which the filmhas been grown. Then, process steps can be controlled easily.

[0032] In the step (c), multivariate analysis may be performed based onthe shapes of the reference infrared-absorption spectra and of theinfrared absorption spectrum, thereby calculating the temperature atwhich the film has been grown. Then, process control can be carried outaccurately.

BRIEF DESCRIPTION OF DRAWINGS

[0033] FIGS. 1(a) and 1(b) are respectively a view showing the infraredabsorption spectra of FSG films and an enlarged view showing parts ofthe spectra in the vicinity of their peaks, measured by FT-IRspectroscopy.

[0034]FIG. 2 is a table showing wavelengths indicating the maximumabsorption values, as well as the maximum absorption values at therespective peaks of the infrared absorption spectra shown in FIGS. 1(a)and 1(b).

[0035] FIGS. 3(a) through 3(c) are respectively views illustratingreference infrared-absorption spectra, and the infrared absorptionspectrum of a film targeted for measurement, and a view indicating amethod for determining a film-growing temperature using PLS regression.

[0036] FIGS. 4(a) through 4(d) respectively show the infrared absorptionspectra of FSG films that have been grown at 380° C., 430° C. and 480°C., and the infrared absorption spectrum of an FSG film targeted formeasurement.

[0037]FIG. 5 shows how to construct a database from theinfrared-absorption spectrum patterns of FSG films.

[0038]FIG. 6 is a flow chart showing a procedure for inferring thefilm-growing temperature of a target film (FSG film) by multivariateanalysis.

[0039]FIG. 7 is a graph showing correlation between film-growingtemperatures in an HDP-CVD apparatus that are inferred by a methodaccording to a second embodiment, and film-growing temperatures measuredby a method based on a known method.

[0040]FIG. 8 is a cross sectional view showing the structure of asemiconductor device formed in a third embodiment.

[0041]FIG. 9 is a flow chart illustrating process steps before and afteran FSG film is formed in the fabrication procedure of the thirdembodiment.

[0042]FIG. 10 shows the dependency of FSG-film etch rate on film-growingtemperature.

[0043]FIG. 11 shows data illustrating temperature distribution in awafer face, obtained for an FSG film that has been formed using anHDP-CVD apparatus.

[0044] FIGS. 12(a) and 12(b) are respectively tables showing exemplarysettings in a constructed database and a calculation result.

[0045]FIG. 13 is a table showing results of examination of temperaturesin the constructed database and analysis temperatures.

BEST MODE FOR CARRYING OUT THE INVENTION

[0046] Used in the following embodiments are techniques of measuring, byFT-IR (Fourier-transform infrared) spectroscopy, the infrared absorptionspectrum of a substrate on which a film is formed, and of performingmultivariate analysis of the infrared absorption spectrum based onpattern recognition, using PLS (partial least squares) regression.

[0047] First Embodiment

[0048] FIGS. 1(a) and 1(b) are respectively a view showing the infraredabsorption spectra of FSG (fluorine-containing silicon oxide) films andan enlarged view showing parts of the spectra in the vicinity of theirpeaks, measured by FT-IR spectroscopy using the film-growing temperaturein an HDP-CVD apparatus as a parameter.

[0049] The infrared absorption spectra of the FSG films shown in FIGS.1(a) and 1(b), which are the infrared absorption spectra of FSG filmsgrown on respective silicon substrates, are measured by the followingprocedure.

[0050] Silicon substrates are in general permeable to infraredradiation. When one face of a silicon substrate is irradiated withinfrared radiation, a certain proportion of the infrared radiation isabsorbed by the silicon substrate, following which the infraredradiation that has permeated the silicon substrate is transmittedthrough the other face of the silicon substrate. Taking advantage ofthis property, the reverse or obverse face of a wafer is irradiated withinfrared coherent light with a diameter of some 5 mm, for example, inthe perpendicular direction. Using FT-IR spectroscopy, coherent lightbetween the intensity of the incident infrared radiation and theintensity of the infrared radiation that has transmitted through thewafer is detected; and a function for the intensity of the coherentlight in relation to the optical path difference is Fourier-transformedto calculate a function in relation to the wavenumbers, which becomesthe first infrared absorption spectrum.

[0051] Next, the silicon substrate is placed inside an HDP-CVD apparatusand an FSG film is grown on the silicon substrate to a given thickness.The same spot on the wafer is then irradiated with infrared radiationunder substantially the same conditions as described above. Using FT-IRspectroscopy, the ratio of the intensity of the infrared radiationincident on the FSG film and the silicon substrate, to the intensity ofthe infrared radiation that has permeated both the film and substrate ismeasured wavelength by wavelength. This becomes the second infraredabsorption spectrum. The first infrared absorption spectrum issubtracted from the second infrared absorption spectrum to calculate theinfrared absorption of the FSG film alone. In this manner, the infraredabsorption spectrum of the silicon substrate is subtracted from thecombined infrared absorption spectrum of the FSG film and siliconsubstrate, thereby enabling the infrared absorption spectrum of the FSGfilm alone as desired to be obtained.

[0052] In the following description, the infrared absorption spectra ofFSG films are measured by the same procedure, except where specificallynoted. Nevertheless, it should be understood that thin films that aresubjects for measuring infrared absorption spectrum in the presentinvention are not limited to FSG films, nor are the methods forfabricating semiconductor devices limited to methods using an HDP-CVDapparatus. Likewise, the substrate underlying the thin film is notlimited to a silicon substrate. Furthermore, the infrared-absorptionspectrum measurement method is not limited to FT-IR spectroscopy.

[0053] Moreover, if the silicon substrate thickness, phosphorousconcentration and oxygen concentration are identical, the same result asthat acquired when the first infrared absorption spectrum is subtractedfrom the second infrared absorption spectrum, can be obtained bymeasuring the second infrared absorption spectrum alone.

[0054] It should be also understood that in the present invention theinfrared absorption spectra are measured by an infrared spectroscopyanalytical instrument for semiconductor (IR-EPOCH 2000), as an FT-IRbased instrument, manufactured by Newly Instruments, Inc.

[0055] As can be seen from FIGS. 1(a) and 1(b), if the FSG film-growingtemperatures differ, the resultant infrared absorption spectra differ inshape; in particular, the maximum absorption values and the wavelengthsthat indicate the maximum absorption values differ in the peak regions.The present inventors made various studies as to whether there might bea method, other than the above-mentioned known temperature-measurementmethod based on the rate at which an amorphous silicon film isrecovered, for monitoring film-growing temperature in an HDP-CVDapparatus. The cumulative result of their studies was the discoveringthat infrared absorption spectra (which in this embodiment are theinfrared absorption spectra measured by FT-IR spectroscopy) differdepending on the thin-film growing temperature (which in this embodimentis the film-growing temperature in an HDP-CVD apparatus).

[0056] It will be described why infrared absorption spectra measured byFT-IR spectroscopy differ depending on the film growing temperature inan HDP-CVD apparatus.

[0057] An FSG film formed in an HDP-CVD apparatus presumably becomes amore perfect silicon oxide film as the film-growing temperature israised. Specifically, analysis, by FT-IR spectroscopy, of FSG films thathave been grown to the same thickness at different temperatures hasresulted in the findings of: (1) the existence of a variation (α_(a))between the heights of the peaks, which is caused by difference indegree as to how perfect the resultant FSG films are, each peak showingthe total amount of absorption by, e.g., Si—O bonds (see FIG. 1(a)); and(2) the existence of a difference (α_(b)) between the locations of thepeaks for, e.g., the Si—O bonds, which difference is created by qualityvariations between the FSG films due to the different film-growingtemperatures (see FIG. 1(b)).

[0058]FIG. 2 is a table showing wavelengths indicating the maximumabsorption values, as well as the maximum absorption values at therespective peaks of the infrared absorption spectra shown in FIGS. 1(a)and 1(b). In the range shown in FIG. 2, as the film-growing temperaturesare raised, both the maximum absorption values and the wavenumbersindicating the maximum absorption values increase.

[0059] More specifically, the present inventors noted that the FSG filmsthat have been grown at different temperatures differ from each other inthe height and location of their peaks for, e.g., the Si—O bonds, thatis, in the shape of the absorption peaks, resulting in the discovery ofthe fact that film-growing temperatures in an HDP-CVD apparatus can bedetected using a new, unconventional method using FT-IR spectroscopy.The reason why the different film-growing temperatures result in thedifferent absorption spectrum shapes is presumably that bonds such asSi—O, Si═O and Si≡O in the silicon oxide exist in different proportionsdepending the film-growing temperature.

[0060] Subsequently, it will be described how to analyze differentinfrared absorption spectra for a thin-film growing temperature. Ananalytical technique based on pattern recognition using PLS regressionis used in this embodiment for the analyzing of different infraredabsorption spectra for a film-growing temperature.

[0061] FIGS. 3(a) and 3(b) are views illustrating referenceinfrared-absorption spectra, and the infrared absorption spectrum of afilm targeted for measurement (which will be referred to as a“target-film infrared absorption spectrum”,) in an analytical model ofmultivariate analysis technology based on pattern recognition, and FIG.3(c) is a view indicating a method for determining a film-growingtemperature using PLS regression. In FIGS. 3(a) and 3(b), peaks Oindicate peaks of absorption by, e.g., SiO₂, and peaks F indicate peaksof absorption by SiF. As shown in the figures, distance between thepeaks O and the associated peaks P change depending on the film-growingtemperature.

[0062] First, as shown in FIG. 3(a), the reference infrared-absorptionspectrum patterns, SPT₁, SPT₂, and SPT₃ of multiple FSG films (threefilms in this embodiment) that have been formed at mutually differentfilm-growing temperatures (T1<T2<T3) are previously measured using FT-IRspectroscopy and stored as a database in a storage device.

[0063] A target-film infrared-absorption spectrum pattern SPT_(A) isthen measured as shown in FIG. 3(b).

[0064] FIGS. 4(a) through 4(d) respectively show the infrared absorptionspectra of FSG films that have been grown at 380° C., 430° C. and 480°C., and the infrared absorption spectrum of an FSG film targeted formeasurement. Specifically, FIGS. 4(a) through 4(c) show specificexamples of the infrared-absorption spectrum patterns SPT₁, SPT₂ andSPT₃, shown in FIG. 3(a), for the three FSG films that have been grownat mutually different temperatures. FIG. 4(d) shows a specific exampleof the target-film infrared-absorption spectrum pattern SPT_(A) shown inFIG. 3(b).

[0065] Subsequently, pattern analysis is carried out to obtain a valueX_(i) ² by the following equation (1), the value X_(i) ² being the sumof squares of the difference between each of the three referenceinfrared-absorption spectrum patterns SPT₁, SPT₂, and SPT₃, and thetarget-film infrared-absorption spectrum pattern SPT_(A).

X _(i) ²=Σ(SPT _(i) −SPT _(A))²   (1)

[0066] In Σ(SPT_(i)−SPT_(A))² on the right side of the equation (1), thedifference in absorption, at each wavelength, between each referenceinfrared-absorption spectrum pattern and the target-filminfrared-absorption spectrum pattern, is squared and integrated for eachwavelength. That is, from the right side of the equation (1), the sum ofsquares of the differences is obtained. The value X_(i) ² in theequation (1) includes a pattern deviation resulting from, e.g., thedifference in maximum absorption value at the peak, and in wavelengthindicating the maximum absorption value, between each referenceinfrared-absorption spectrum pattern and the target-filminfrared-absorption spectrum pattern, and from the difference in thedistance between each peak O and its associated peak F shown in FIG.3(a).

[0067] Consequently, as shown in FIG. 3(c), three points X₁ ², X₂ ² andX₃ ² representing the sums of squares of the differences are obtained,thereby determining a curve L_(A) (a quadratic curve in this example forthe sake of simplicity) that passes through the three points X₁ ², X₂ ²and X₃ ². From this curve L_(A), a temperature T_(A) at which the sum ofsquares of the differences X² becomes the minimum, is found. Thistemperature is estimated as the film-growing temperature of the FSGfilm. The following describes a specific example of this procedure.

[0068] FIGS. 12(a) and 12(b) are respectively tables showing exemplarysettings in a constructed database and a calculation result. In a PLSregression solution technique, a solution is obtained by a numericalcomputation technique using a computer, and the parameters are adjustedso that the correct coefficient for the temperature in the database whenmultiple regression analysis is performed based on PLS regression, withrespect to the PLS model of the database, is close to 1.0. According tothe results of numerical computation performed by the present inventorson this occasion, when an infrared absorption spectrum in the range froma maximum wavenumber of 1600 cm⁻¹ to a minimum wavenumber of 700 cm⁻isused, and the number of divisions for the infrared absorption spectrumis set to 467, the resultant correct coefficient is highest, yielding a0.98 correct coefficient.

[0069]FIG. 13 is a table showing the results of examination oftemperatures in the constructed database and analysis temperatures.Shown in FIG. 13 are temperatures in the database (corresponding to thefilm-growing temperatures Ti associated with the spectrum patternsSPT_(i) shown in FIG. 3(a)); analysis temperatures (corresponding to thefilm-growing temperature T_(A) shown in FIG. 3(c)); differences(difference between the temperature in the database and the analysistemperature); error rates (obtained by multiplying by 100 the quotientobtained by diving the difference with the associated temperature in thedatabase); spectral residuals (corresponding to X² in FIG. 3(c)); andreliability of the analysis values.

[0070] In FIG. 13, it is more preferable that the spectral residuals andthe reliability of the analysis values be as small as possible, and inwhich case, the reliability of the analysis temperatures heightens. Asshown in the figure, the values indicating the spectral residuals andthe reliability of the analysis temperatures, are sufficiently smallwith respect to the setting temperatures in the database, and thus canbe judged to present no practical problem. Further, the results of theexaminations using the database prepared on this occasion show that theerror rates for the FSG-film growing temperatures are not more than±1.0%. Specifically, a PLS model that allows temperatures in the rangeextending from 384.2° C. to 504.5° C. to be estimated within ±1.0%accuracy, is obtained from the calculation results.

[0071] Second Embodiment

[0072] For easy understanding, a method for estimating, as a parameter,film-growing temperature alone is described in the foregoing example.However, thin films formed in the actual process do not have constantthickness and constant impurity concentration (e.g., fluorineconcentration), for example, such that there are variances in theseparameters between wafers or in a wafer. The thickness orimpurity-concentration variance may cause deterioration in the accuracyof film-growing temperature estimation. In the actual process, it isthus necessary to perform multivariate analysis using parametersincluding, e.g., thickness and impurity concentration even if thepurpose is to estimate film-growing temperature.

[0073] Next, it will be described how to estimate various parametersincluding not only the film-growing temperature of a thin film but alsothe quality and thickness thereof. In the following description, theinfrared-absorption spectrum patterns of FSG films that have been grownin an HDP-CVD apparatus are used as an example.

[0074]FIG. 5 shows how to construct a database from theinfrared-absorption spectrum patterns of FSG films. Prepared first arematrixes in which film-growing conditions are expressed. Thefilm-growing conditions, which determine FSG-film quality, includefilm-growing temperature in an HDP-CVD apparatus, fluorine concentrationin FSG films, and the thicknesses of the FSG films. For each of thesecondition categories, a plurality of conditions (three conditions, forexample) are established in the matrixes. FSG films are grown inaccordance with all conditions in the matrixes, and the infraredabsorption spectra of the films are measured by FT-IR spectroscopy,thereby constructing a database from the infrared-absorption spectrumpatterns.

[0075] In the example shown in FIG. 5, twenty-seven infrared-absorptionspectrum patterns in total are complied into the database with respectto the three different thicknesses 300 nm, 600 nm and 900 nm, the threedifferent film-growing temperatures 370° C., 430° C. and 490° C., andthe three different fluorine concentrations 0.4%, 1.4% and 2.4%. Alsoillustrated in the figure are the infrared-absorption spectrum patternsof the films obtained under respective conditions k2 and k3 in which thethickness of each film is 600 nm, the film-growing temperature of eachfilm is about 370° C., while the fluorine concentrations arerespectively about 1.4% and about 2.4%.

[0076] Subsequently, the thickness, film-growing temperature andfluorine concentration of a target film for measurement are computedfrom the infrared-absorption spectrum pattern that the target filmshows, using the various parameters in the database shown in FIG. 5. Inthe computation process, multivariate analysis is performed by aprocedure as is shown in FIGS. 3(a) and 3(b), thereby finally obtainingin a multi-dimensional space numerous points X_(i) ² such as shown inFIG. 3(c), each indicating a sum of squares of differences. In thiscase, since multi-dimensional analysis has to be carried out, results ofthe analysis cannot be presented in graphical form such as is shown inFIG. 3(c). A multi-dimensional figure that is most likely to passthrough these numerous points X_(i) ² is then obtained. The filmthickness, film-growing temperature and fluorine concentration at thepoint indicating the minimum value in this multi-dimensional figure arecomputed as the thickness, film-growing temperature and fluorineconcentration of the target film.

[0077] Instead of the above-mentioned estimation method, three graphs inwhich the abscissas represent the film-growing temperature, thicknessand fluorine concentration, respectively, may be prepared, and in thegraphs, a location X on the abscissa, which represents the minimum valueon a quadratic curve passing through numerous points X_(i) ², may beapproximated to the film-growing temperature, thickness or fluorineconcentration of the target film.

[0078] As has been mentioned above, a solution model of a multivariateanalysis technique based on pattern recognition can be used to inferwhich infrared-absorption spectrum pattern in the constructed databaseis closest to the infrared-absorption spectrum pattern of the targetfilm, thereby obtaining the film-growing temperature, fluorineconcentration and thickness thereof, using the multivariate analysistechnique.

[0079]FIG. 6 is a flow chart showing a procedure for inferring, bymultivariate analysis, the film-growing temperature of a target film(FSG film) for measurement.

[0080] First, in step ST11, reference infrared-absorption spectrumpatterns (for example, patterns with respect to the twenty-seven kindsof conditions shown in FIG. 6) are prepared and stored as a database ina storage device.

[0081] Next, in step ST12, the infrared-absorption spectrum pattern ofthe target film is measured using FT-IR spectroscopy. In should beunderstood that a method other than FT-IR spectroscopy may be used forthe measurement of the infrared-absorption spectrum patterns in thepresent invention.

[0082] Then, in step ST13, multivariate analysis is performed. Obtainedin the example shown in FIGS. 2(a) through 2(c) is the value X_(i) ²that corresponds to the sum of squares of the difference between each ofthe three reference infrared-absorption spectrum patterns SPT₁, SPT₂,and SPT₃, and the infrared-absorption spectrum pattern SPT_(A) of thetarget film. On the other hand, performed in this embodiment is analysis(multivariate analysis) in which the difference in absorption value, ateach wavelength, between each of the twenty-seven referenceinfrared-absorption spectrum patterns and the target-filminfrared-absorption spectrum pattern, is squared and integrated for eachwavelength.

[0083] Subsequently, in step ST14, the film-growing temperature andother factors are computed based on the pattern analysis results. In thefirst embodiment, the temperature T_(A) at which the sum of squares ofthe differences X² becomes the minimum is obtained from the curve L_(A)that passes through the three points X₁ ², X₂ ² and X₃ ² shown in FIG.3(c), and this temperature is computed as the film-growing temperatureof the FSG film. In this embodiment, however, the twenty-seven pointsX_(i) ² that represent the sums of squares of the differences like thepoints shown in FIG. 3(c), are obtained in a multi-dimensional space,such that a multi-dimensional figure which is most likely to passthrough the points X_(i) ² is obtained. The film-growing temperature atthe point indicating the minimum value in the multi-dimensional figureis computed as the film-growing temperature of the target film.

[0084]FIG. 7 is a graph showing correlation between film-growingtemperatures in an HDP-CVD apparatus that are inferred by the method ofthis embodiment, and film-growing temperatures measured by a methodbased on the technique described in International Publication No.WO99/57146. Considering that with the method described in InternationalPublication No. WO99/57146, in the case of temperatures at or below 500°C., it is difficult to determine the rate at which an amorphous layer isrecovered, the other method based on the described technique is used. Asshown in FIG. 7, the film-growing temperatures in the present inventionand the film-growing temperatures obtained by applying the known methodhave a correlation of almost 1:1. This correlation shows that theresults of the measurement, by FT-IR spectroscopy, of the film-growingtemperatures in the HDP-CVD are good.

[0085] In accordance with this embodiment, the film-growing temperatureof a thin film can be measured accurately by performing multivariateanalysis using, as parameters, for example, the thin film's thickness,impurity concentration and film-growing temperature obtained by FT-IRspectroscopy. In particular, as described above, with the techniquedescribed in International Publication No. WO99/57146, it is difficultto measure film-growing temperatures at or below 500° C. In contrast,film-growing temperatures at or below 500° C. can be measured by themethod of the present invention, and in addition, the measurements areperformed easily and quickly (specifically, in a few minutes) by theinventive method.

[0086] It should be noted, however, that the range of film-growingtemperatures measurable by the temperature measuring method of thepresent invention is not limited by 500° C. or less. The range offilm-growing temperatures measurable by the inventive method includessubstantially the same range for the technique described inInternational Publication No. WO99/57146, and further includes lowertemperature ranges. In recent years, as the semiconductor fabricationprocess has been performed at lower temperatures, the present inventionparticularly can exhibit the remarkable effect of being able to measuretemperatures in the 350° C.-to-500° C. process-temperature range, whichis the range in which the semiconductor-device wiring process is carriedout.

[0087] Moreover, in the inventive method, the temperature at which afilm has been grown can be easily measured by performing in-linemonitoring of the infrared absorption spectrum while a film-growingapparatus is used under the same conditions as in the process, thusenabling the film-growing temperatures in all film-growing processes tobe measured without causing any deterioration in productivity.

[0088] Third Embodiment

[0089] As an exemplary application of the thin-film evaluation method ofthe present invention, it will be described how to fabricatesemiconductor devices on production lines.

[0090]FIG. 8 is a cross sectional view showing the structure of asemiconductor device formed in a third embodiment. A trench isolationregion 12 which defines an active region is formed in a siliconsubstrate 11. Many MISFETs 13 are formed in the active region surroundedwith the trench isolation region 12. Formed on the respective upperportions of a source/drain region (not shown) and a gate electrode ofeach MISFET 13 are silicide layers 14 a and 14 b formed by a salicideprocess.

[0091] In the fabrication method of this embodiment, a first interleveldielectric film 20 of a BPSG film is first deposited on the siliconsubstrate 11 on which the numerous MISFETs 13 have been formed. Thefirst interlevel dielectric film 20 has a thickness of about 800 nm.

[0092] Formed next are contact holes which go through the firstinterlevel dielectric film 20 to reach the associated silicide layers 14a and 14 b of the source/drain regions and the gate electrodes. Thecontact holes are then filled with tungsten (W), thereby forming plugs24. Although plugs on the gate electrodes are not shown in FIG. 8, theplugs that are connected to the gate electrodes appear in a crosssection other than the cross section shown in FIG. 8. Each plug 24 has adiameter of about 0.25 μm.

[0093] Next, an Al film is deposited on the first interlevel dielectricfilm 20 and then patterned, thereby forming Al interconnects 33(first-layer interconnects) that are connected to the plugs. Thethickness of the Al interconnects 33 is about 400 nm. Thereafter, asecond interlevel dielectric film 30 is deposited on both the firstinterlevel dielectric film 20 and the Al interconnects 33. The secondinterlevel dielectric film 30 includes a lower film 31 of an FSG filmand an upper film 32 of a P-TEOS film (plasma TEOS film). Thethicknesses of the lower film 31 and the upper film 32 are about 500 nmand about 300 nm, respectively.

[0094] Now, in the present invention, before the lower film 31 of thesecond interlevel dielectric film 30 is deposited, a region to bemeasured (measuring region) in the wafer is irradiated with an infraredbeam in order to measure the infrared absorption spectrum of the entiresubstrate underlying the lower film 31. The lower film 31 is thendeposited by an HDP-CVD process. The lower film 31 of an FSG film isgrown under the conditions that the pressure inside a chamber of afilm-growing apparatus is 6 mTorr (about 0.8 Pa); the RF power of aplasma CVD apparatus is 900W/2300W; the bias power is 2350W; the Hepressure on the bottom face of the wafer is 2 mTorr (about 0.27 Pa) onthe IN side; the TOP flow rate of argon gas is 9 (ml/min); the SIDE flowrate of the argon gas is 46 (ml/min); the TOP flow rate of oxygen is 53(ml/min); the SIDE flow rate of the oxygen is 73 (ml/min); the TOP flowrate of silane is 4 (ml/min); the SIDE flow rate of the silane is 40(ml/min); and the TOP flow rate of silicon tetrafluoride is 28 ml/min.

[0095] After the lower film 31 is deposited, the measuring region of thewafer is irradiated with infrared radiation in order to measure theinfrared absorption spectrum. From the difference between both infraredabsorption spectra, the infrared absorption spectrum of the lower film31 alone is measured. Further, using the reference infrared-absorptionspectrum patterns described in the second embodiment (see FIG. 5),multivariate analysis of the infrared-absorption spectrum pattern of thelower film 31 is performed using the film-growing temperature, filmthickness and fluorine concentration as parameters. In this manner, thefilm-growing temperature, thickness and fluorine concentration of thelower film 31 are measured to determine whether the conditions for thedeposition of the lower film 31 are appropriate or not.

[0096] Subsequently, after the upper film 32 of the second interleveldielectric film 30 is deposited, via holes are formed in the secondinterlevel dielectric film 30 so as to reach the Al interconnects 33 onthe first interlevel dielectric film 20. The via holes are then filledwith tungsten (W), thereby forming plugs 34. The upper film 32 of thesecond interlevel dielectric film 30 has a thickness of about 300 nm,and the plugs 34 have a diameter of about 0.3 μm.

[0097] Thereafter, Al interconnects 43 (second-layer interconnects) anda third interlevel dielectric film 40 are formed on the secondinterlevel dielectric film 30 by the same procedure as described above.The third interlevel dielectric film 40 includes a lower film 41 of anFSG film and an upper film 42 of a P-TEOS film. When the lower film 41is formed, multivariate analysis using the infrared absorption spectrais performed in order to control the film-growing temperature, filmthickness and fluorine concentration, for example.

[0098] Al interconnects 53 (third-layer interconnects) and a forthinterlevel dielectric film 50 are then formed on the third interleveldielectric film 40 by the same procedure as described above. The fourthinterlevel dielectric film 50 includes a lower film 51 of an FSG filmand an upper film 52 of a P-TEOS film. When the lower film 51 is formed,multivariate analysis using the infrared absorption spectra is performedin order to control the film-growing temperature, film thickness andfluorine concentration, for example.

[0099] Al interconnects 63 (fourth-layer interconnects) and apassivation film 60 of a P—SiN film are then formed on the forthinterlevel dielectric film 50.

[0100] In this embodiment, multivariate analysis utilizing infraredabsorption spectra is not performed to measure the film-growingtemperatures of the first interlevel dielectric film 20 of a BPSG film,the respective upper films 32, 42 and 52 of the second through fourthinterlevel dielectric films of a P-TEOS film, and the passivation film60 of a P—SiN film. The reason for this is as follows. Used for BPSGfilms, P-TEOS films and P—SiN films is not an HDP-CVD apparatus usinghigh-density plasma, but a CVD apparatus utilizing normal plasma orthermal reaction, which does not have a mechanism, such as found in anHDP-CVD apparatus, in which an electrostatic chuck is employed to holdthe wafer and the reverse face of the wafer is cleaned with He. Thisstructure allows a thermocouple to be embedded in a lower electrode in aconventional plasma CVD apparatus in order to measure the temperature ofthe lower electrode, for example, thereby indirectly measuring the wafertemperature. Note that if multivariate analysis based on infraredabsorption spectra is performed when films, such as BPSG films, P-TEOSfilms and P—SiN films, are formed, impurity concentration (e.g., boronor phosphorous concentration in a BPSG film) and film thickness can alsobe measured, enabling process steps to be strictly controlled.

[0101] Also, the trench isolation region 12 may be made of USG (undopedsilicate glass) deposited using an HDP-CVD apparatus, and thusmultivariate analysis based on infrared absorption spectra may also beperformed for the trench isolation region 12.

[0102]FIG. 9 is a flow chart illustrating process steps before and afteran FSG film is formed in the fabrication procedure of this embodiment.

[0103] First, in step ST21, the infrared absorption spectrum of anunderlying wafer is measured. In the case of forming the lower film 31of the second interlevel dielectric film 30, the underlying wafercorresponds to the wafer on which the first interlevel dielectric film20 and the plugs 24 have already been formed. In the case of forming thelower film 41 of the third interlevel dielectric film 40, the underlyingwafer corresponds to the wafer on which the second interlevel dielectricfilm 30 and the plugs 34 have already been formed. In the case offorming the lower film 51 of the fourth interlevel dielectric film 50,the underlying wafer corresponds to the wafer on which the thirdinterlevel dielectric film 40 and the plugs 44 have already been formed.

[0104] Next, in step ST22, an FSG film (which in this embodiment is eachof the lower films 31, 41 and 51) is deposited using an HDP-CVDapparatus under the above mentioned conditions.

[0105] The infrared absorption spectrum of the wafer after the FSG filmhas been deposited is then measured in step ST23. That is, theabsorption spectrum for infrared radiation that is transmitted throughboth the FSG film and the underlying wafer, is measured.

[0106] Subsequently, in step ST24, the difference between the infraredabsorption spectra measured in steps ST23 and ST21 is computedwavelength by wavelength, thereby preparing the infrared-absorptionspectrum pattern of the FSG film alone.

[0107] Then, in step ST25, multivariate analysis is carried out inaccordance with the method described in the second embodiment, usingreference infrared-absorption spectrum patterns (for example, numerousspectrum patterns in which film-growing temperature, film thickness andfluorine concentration such as shown in FIG. 5 are used as parameters)pre-stored in a database. As a consequence, a graph or a function thatreplaces the curve shown in FIG. 3(c) with a multi-dimensional figure ormulti-dimensional function, is obtained.

[0108] In step ST26, from the multi-dimensional figure ormulti-dimensional function obtained in step ST25, the film-growingtemperature, film thickness and fluorine concentration, e.g., of the FSGfilm that give the minimum value in the multi-dimensional figure orfunction, are inferred.

[0109] Thereafter, in step ST27, it is determined whether thefilm-growing temperature, film thickness and fluorine concentrationinferred in step ST26 are within proper range or not. If thefilm-growing temperature is too low, the contact (specifically thecontact resistance) between the plugs formed in the interleveldielectric film located under the FSG film, and the conductor layer incontact with and located under the plugs, may deteriorate. Anexcessively low film-growing temperature may also cause the followingdrawbacks.

[0110]FIG. 10 shows the dependency of FSG-film etch rate on film-growingtemperature. In FIG. 10, the ordinate represents the etch rate as aratio to the etch rate of a thermal oxide film. As shown in FIG. 10, anexcessively low film-growing temperature results in a high etch rate,leading to difficulty in controlling, e.g., etch time in the processsteps. Specifically, when the etch rate of a thin film increases,drawbacks such as overetching may be caused.

[0111] More specifically, as the quality of an FSG film, e.g., the etchrate may be included in the parameters for multivariate analysis.

[0112] On the other hand, an excessively high film-growing temperaturemay cause deterioration in the characteristics of the Al film that hasbeen formed in the lower portion of the FSG film. In view of this, theFSG-film growing temperature has an appropriate range. In this example,the FSG-film growing temperature is preferably within the range between380° C. or more and 480° C. or less. Further, if the film thickness istoo large, the formation of the via holes and the filling of the plugsbecome difficult, while if the film thickness is too small, capacitybetween interconnects sandwiching an interlevel dielectric film mayincrease, or the insulating property of the interlevel dielectric filmmay deteriorate. The film thickness therefore also has a proper range.Furthermore, an excessively low fluorine concentration may lead to aninsufficiently reduced relative dielectric constant of the interleveldielectric film, while an excessively high fluorine concentration maycause the Al film to be peeled off due to F diffusion. In view of this,the fluorine concentration also has an appropriate range.

[0113] As a result, when the film-growing temperature, film thickness,and fluorine concentration, for example, fall within their respectiveproper ranges, it is possible to directly proceed to the next step. Onthe other hand, if the film-growing temperature, film thickness, andfluorine concentration, for example, fall outside their respectiveproper ranges, it is necessary to go to step ST27, wherein after theconditions in the HDP-CVD are changed, the FSG film is etched away fordeposition of another FSG film.

[0114] It should be understood that after the conditions are changed instep ST27, it is possible to proceed to the next step. Even in thatcase, when the lower film 41 of the third interlevel dielectric film 40is formed after the lower film 31 of the second interlevel dielectricfilm 30 has been formed, the FSG film can be deposited under theappropriate conditions.

[0115] As has been described above, parameters such as the film-growingtemperature, film thickness and fluorine concentration of FSG films areeasily maintained in their respective proper ranges in the semiconductordevice fabrication process, enabling strict and easy control of thesemiconductor device fabrication process. Moreover, yields can beimproved by re-doing formation of a thin film.

[0116] Note that the infrared absorption spectra measured by FT-IRspectroscopy shown in FIG. 1 are the data of the infrared absorptionspectra of the FSG films alone that have been grown in an HDP-CVDapparatus. However, it has been confirmed that with the combinedinfrared absorption spectrum of an FSG film and a silicon substrate, thefilm-growing temperature in an HDP-CVD apparatus can be measured as inthe case shown in FIG. 7.

[0117] In addition, according to the inventive method, since theinfrared-absorption spectrum components of a thin film alone can bemeasured by performing difference computation, not only in-linemonitoring is available, but also the film-growing temperature of anactual device, in which the reverse face of a substrate has acomplicated structure, can be measured accurately.

[0118] Moreover, although FSG films grown in an HDP-CVD apparatus areused in the descriptions in the foregoing embodiments, the presentinvention is also applicable to cases of growing other silicon oxidefilms, such as a phosphorous-doped silicon oxide film (PSG film), aboron/phosphorous-doped silicon oxide film (BPSG film), and a siliconnitride film. Additionally, in the descriptions of the foregoingembodiments, an HDP-CVD apparatus is used to grow silicon oxide filmssuch as FSG films. The present invention is, however, applicable tocases in which other film growing apparatuses, such as a conventionalplasma CVD apparatus (P-CVD) and a low pressure CVD apparatus (LP-CVD),are used to grow films.

[0119] Fourth Embodiment

[0120] In this embodiment, it will be described how to utilizemeasurement of a film-growing temperature in order to measuretemperature inside a chamber.

[0121] As has been described above, since the infrared absorptionspectrum of, e.g., an FSG film can be used to measure the film-growingtemperature, chamber temperature can also be measured. Once the chambertemperature is known, the temperature can be used not only for CVD, butalso for each process in the semiconductor device fabrication procedure.

[0122] Conventionally, temperature inside a chamber has been measuredwith a temperature sensor attached to the bottom face of athermocouple-equipped wafer. Although the use of thethermocouple-equipped wafer allows the temperature of the reverse faceof the wafer to be measured, the temperature of the wafer surface, thatis, the actual temperature at which the amorphous region is subjected toan annealing process, cannot be measured. In addition, the measurabletemperature range is limited and thus measurements of temperatureshigher than a certain level become difficult.

[0123] Also, with the technology described in International PublicationNo. WO99/57146, for temperatures at or below 500° C., the rate at whicha layer is recovered from the amorphous state is unknown. This isbecause at low temperatures, recovery from the amorphous state completesat a very early stage and would not proceed even if further timeelapsed.

[0124] In contrast, the inventive method using infrared absorptionspectra has the advantage of being able to measure any temperatures thatfall within the temperature range in which CVD is possible. Inparticular, the present invention is highly effective in the case oftemperatures at or below 500° C., measurements of which are difficultwith the technology described in International Publication No.WO99/57146.

[0125]FIG. 11 shows data illustrating temperature distribution in awafer face, obtained for an FSG film that has been formed using anHDP-CVD apparatus. Since the diameter of the infrared beam is about 5mm, infrared absorption spectra can be measured with respect to a numberof spots in the wafer. In that case, the spots in the wafer with respectto which infrared absorption spectra have been measured before the filmis formed, have to substantially agree with the spots in the wafer withrespect to which infrared absorption spectra are measured after the filmhas been formed. In this respect, since currently used infraredradiation measuring devices have very improved positioning accuracy,there have been practically no problems.

[0126] As shown in FIG. 11, the temperature distribution in the waferface can be measured by performing multivariate analysis utilizinginfrared absorption spectra in accordance with the present invention.Based on this, temperature distribution in a chamber of a CVD apparatusmay be measured. The wafer used for the temperature measurement may be aproduct wafer on a production line or a control wafer used for procedurecontrol.

[0127] Other Embodiments

[0128] In the foregoing embodiments, target films for measurement areirradiated with infrared radiation in order to measure the infraredabsorption spectra using FT-IR spectroscopy, thereby evaluating thetarget films. The present invention is, however, applicable to cases inwhich other spectroscopic techniques, such as dispersive infraredspectroscopy, laser Raman spectroscopy or X-ray photoelectronspectroscopy, are used to measure an absorption spectrum for observingbonds between the atoms forming a thin film.

[0129] According to the present invention, the growing temperatures orcharacteristics of films can be measured by in-line monitoring of thefilm-growing apparatus, thereby enabling the film growing temperaturesin all film-growing processes to be measured without causing anydeterioration in productivity.

INDUSTRIAL APPLICABILITY

[0130] The present invention is applicable to fabrication of variouskinds of transistors and semiconductor memories and other semiconductordevices that are incorporated into electronic equipment.

1. A film evaluation method comprising the steps of: (a) irradiatingwith electromagnetic waves a substrate on which a film is formed,thereby measuring an absorption spectrum for the electromagnetic waves,and (b) calculating from the shape of the absorption spectrum a specificvalue corresponding to the quality of the film.
 2. The film evaluationmethod of claim 1, characterized in that: in the step (a), theelectromagnetic waves are infrared radiation, and in the step (b), thespecific value is calculated from the shape of an absorption spectrumfor the infrared radiation.
 3. The film evaluation method of claim 2,characterized in that: a plurality of reference infrared-absorptionspectra are prepared in advance in accordance with film quality level,and in the step (b), the reference infrared-absorption spectra and theinfrared absorption spectrum of the film are compared with each other,thereby calculating the specific value.
 4. The film evaluation method ofclaim 3, characterized in that in the step (b), multivariate analysis isperformed based on the shapes of the reference infrared-absorptionspectra and of the infrared absorption spectrum, thereby calculating thespecific value.
 5. The film evaluation method of any one of claims 1through 4, characterized in that: in the step (a), an infraredabsorption spectrum of the substrate, which has been measured inadvance, is subtracted from the infrared absorption spectrum of the filmand the substrate, thereby obtaining an infrared absorption spectrum ofthe film alone.
 6. A temperature measuring method comprising the stepsof: (a) irradiating with electromagnetic waves a substrate on which afilm is formed, thereby measuring an absorption spectrum for theelectromagnetic waves, and (b) calculating from the shape of theabsorption spectrum a temperature at which the film has been grown. 7.The temperature measuring method of claim 6, characterized in that: inthe step (a), the electromagnetic waves are infrared radiation, and inthe step (b), the temperature at which the film has been grown iscalculated from the shape of an absorption spectrum for the infraredradiation.
 8. The temperature measuring method of claim 7, characterizedin that: a plurality of reference infrared-absorption spectra areprepared in advance in accordance with film-growing temperature, and inthe step (b), the reference infrared-absorption spectra and the infraredabsorption spectrum of the film are compared with each other, therebycalculating the temperature at which the film has been grown.
 9. Thetemperature measuring method of claim 8, characterized in that in thestep (b), multivariate analysis is performed based on the shapes of thereference infrared-absorption spectra and of the infrared absorptionspectrum, thereby calculating the temperature at which the film has beengrown.
 10. The temperature measuring method of any one of claims 6through 9, characterized in that in the step (a), an infrared absorptionspectrum of the substrate, which has been measured in advance, issubtracted from the infrared absorption spectrum of the film and thesubstrate, thereby obtaining an infrared absorption spectrum of the filmalone.
 11. The temperature measuring method of any one of claims 6through 10, characterized in that: in the step (a), the substrate isplaced in a film-growing apparatus in advance, and the film is formed onthe substrate, and in the step (b), the temperature at which the filmhas been grown is calculated as a temperature inside the film-growingapparatus.
 12. A method for fabricating a semiconductor device includinga film as an element forming the device, the method comprising the stepsof: (a) forming the film on an underlying wafer placed in a film-growingapparatus, (b) irradiating with infrared radiation the wafer on whichthe film has been formed, thereby measuring an infrared absorptionspectrum, (c) calculating from the shape of the infrared absorptionspectrum a specific value corresponding to the quality of the film, and(d) controlling conditions determined for the film-growing apparatus, inaccordance with the specific value calculated in the step (c).
 13. Thesemiconductor fabrication method of claim 12, characterized in that: aplurality of reference infrared-absorption spectra are prepared inadvance in accordance with film quality level, and in the step (c), thereference infrared-absorption spectra and the infrared absorptionspectrum of the film measured in the step (b) are compared with eachother, thereby calculating the specific value.
 14. The semiconductorfabrication method of claim 13, characterized in that in the step (c),multivariate analysis is performed based on the shapes of the referenceinfrared-absorption spectra and of the infrared absorption spectrum,thereby calculating the specific value.
 15. A method for fabricating asemiconductor device including a film as an element forming the device,the method comprising the steps of: (a) forming the film on anunderlying wafer placed in a film-growing apparatus, (b) irradiatingwith infrared radiation the wafer on which the film has been formed,thereby measuring an infrared absorption spectrum, (c) calculating fromthe shape of the infrared absorption spectrum a temperature at which thefilm has been grown, and (d) controlling conditions determined for thefilm-growing apparatus, in accordance with the temperature at which thefilm has been grown, the temperature calculated in the step (c).
 16. Thesemiconductor fabrication method of claim 15, characterized in that: aplurality of reference infrared-absorption spectra are prepared inadvance in accordance with film-growing temperature, and in the step(c), the reference infrared-absorption spectra and the infraredabsorption spectrum of the film measured in the step (b) are comparedwith each other, thereby calculating the temperature at which the filmhas been grown.
 17. The semiconductor fabrication method of claim 16,characterized in that in the step (c), multivariate analysis isperformed based on the shapes of the reference infrared-absorptionspectra and of the infrared absorption spectrum, thereby calculating thetemperature at which the film has been grown.